To perform a Master Reset on your Garmin Astro 430 please follow these steps
  1. Start with your Astro 430 switch OFF
  2. Press and hold down the Map and Enter buttons simultaneously and press and release the Power Button
 
  1. Continue to hold down Map and Enter until you see a screen come up that asks: "Do You Really Want To Erase All User Data?"
  1. Select YES and your device will reboot, you can now remove your fingers from Map and Enter.